1. Field of the Invention
The present invention relates to the field of semiconductor processing and more specifically to novel contact and via structures and their method of fabrication.
2. Discussion of Related Art
Modern integrated circuits and memory devices include multiple levels of metalization separated by insulating layers. The normal method of making contact from one metalization layer to another is to use photoresist as a mask and to dry etch the insulators stopping on the underlying conductor. Once an opening is formed this way, then the opening is filled with a second deposited conductor. Today the conductor is usually chemical vapor deposited (CVD) tungsten because the sidewall slopes are too steep for a sputtered metal to cover. Historically, people use trick etches of the insulator to provide a slope on the sidewalls so that the sputter metals could cover the sidewall and therefore not need CVD metal deposition. It is to be appreciated that presently low resistance metals such as aluminum is typically be deposited by sputtering and not by CVD. Today, however, people have gone away from slope sidewalls because the process is hard to control and because the area required to make the contact is too large.
The present invention is a contact/via and its method of fabrication. The contact/via of the present invention is formed on a first conductive film. The contact has a first sidewall and a second sidewall wherein the first sidewall is opposite the second sidewall. The first sidewall has a stair step configuration such that the first sidewall is closer to the second sidewall at the bottom of the contact than at the top of the contact. A second conductive film is formed on the stair step sidewall on the conductive film.